At about 8:45 p.m. on Saturday, the women were walking north in the 400 block of Maple Avenue when the suspects approached them, South San Francisco police said.
The victims tried to cross the street but were stopped by the suspects, both of whom were carrying handguns, according to police.
The gunmen told the women to be silent and hand over their property, police said. The victims complied and were then ordered to turn and walk in the opposite direction.
The suspects were last seen running north on Maple Avenue.
No one was injured.
The robbers were described as black or Hispanic males in their late teens or early 20s, police said. One was wearing a gray hoodie and dark-colored pants. The second suspect was wearing a black beanie, black hoodie and dark jeans.
On Friday, a woman was robbed as she was getting into her car on Terminal Court just before noon, police said.
The woman was on her way to make a bank deposit for her employer, and was robbed of cash and checks, police said.
The assailant threatened to shoot the woman if she didn't hand over her purse, police said.
There is no immediate indication that the two crimes are related, Sgt. Bruce McPhillips said.
Anyone with information about the robberies is asked to contact South San Francisco police at (650) 877-8900.